Thrombin accumulation in brains of patients with Alzheimer's disease.

Thrombin was detected immunohistochemically in brain tissue of Alzheimer's disease (AD) patients and age-matched controls. Positive staining was restricted to vessels and residual plasma in controls but was also present in senile plaques, some diffuse amyloid deposits and neurofibrillary tangles in AD. Positive staining was abolished by absorption of antibody with purified human thrombin but not by absorption with prothrombin. The data suggest that thrombin formation from prothrombin probably takes place in AD brain.